I'm currently doing research to transition a corporate website that features 10,000 static pages and needs to be converted to a dynamic CMS. My basic instructions are to purchase a solid system which is easy to use.

I have spoken with and demo'd a number of paid vendors. I'd like to solicit some feedback on these.

Has anyone here had personal experience with any of the following?

Sitecore

Episerver

Alterian

Ektron

Autonomy (Interwoven)

Open Text (Vignette)

What is your general opinion and what was the transition like to adopt that system?

Have you checked out ExpressionEngine? It can handle quite large sites and is very easy to use. (Maybe you are looking for something altogether bigger, but I thought I'd mention this one, as it's worth a look. It's been used to run some pretty enormous sites.)